Planning the Electrics/Electronics - Domestic System Part 1

Soon it will be time to install the electrics. Let’s start with the various application types of batteries. There are two types:     

  Starting batteries are designed to provide a big jolt of electrical power (or amperes) for a short period of time, then be quickly recharged. 

  Deep-cycle batteries (or House/Domestic/Leisure electrics battery) are built to supply a limited number of amps over a longer time and then be recharged more slowly. 

I will use AGM (absorbed glass mat) Batteries, explained below. 

The Domestic Electrics/Electronics
 At this stage I will ignore the Starting battery side until I have the Outboard Motor: the motor I will choose specifies the exact battery it needs.

   I will begin with the 'domestic/leisure' side of the equation: that is the battery that powers all the devices like lights, bilge pump, etc. Therefore, I will need to list the devices I mean to use and the power they will draw in Amps.

Most devices have the Amperage printed on them, if not you can use the table I add at the end of this post.

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Calculating Ampere Hours Required (Ah)

         Device                         Amps          

1.   Bilge Pump                      3

2.   Dragonfly-5                     0.8

3.   Cockpit Light                   0.1

4.   Nav Lights                       3.7  

5.   2 Windscreen Wipers       2.0

6.   VHF  Radio                      1.2

                                       ________

Total Amps                           10.8  

Although it is unlikely that all the devices will be operating at the same time, especially continuously for 10 hours, we must cater for the maximum use for 10 hours - which we calculate thus:

                  10 x 10.8 = 108 Amp Hours (Ah)

So we need to find a (domestic/Leisure) battery capable of supplying at least, say, 110 Ah.

Battery Choice

I have selected a battery, Cost £160 (US$210), it's the:

12V 120AH LEOCH ADVENTURER AGM LEISURE BATTERY (LAGM120)

 Which satisfies the Ah I need.

It is a Absorbed Glass Mat (AGM) battery which is  dry-cell, with the battery acid being encapsulated in fibreglass sheets. In comparison to flooded batteries, AGMs offer increased levels of reliability and versatility – with no free acid, they can be mounted in any orientation and are better able to handle vibration.

See Link> https://www.alpha-batteries.co.uk/120ah-leoch-agm-leisure-battery/

Battery Location on Boat

The battery will be stowed in the aft starboard locker, the one nearest us in the picture below. Retaining straps have already purchased and will be shown during fitting.

This battery will need  special charging equipment.

Charging  the Battery -Ashore:

Costing £65 (US$85), I selected the charger shown as an accessory to the above battery.

12V 10A 7 STAGE CONNECT & FORGET AUTOMATIC BATTERY CHARGER WITH UK PLUG

See the Link for details> https://www.alpha-batteries.co.uk/catalog/product/view/id/598/s/12v-10a-connect-forget-leisure-battery-charger/category/148/

Ah Table